Method of interrogating a barcode

ABSTRACT

Presented is a system and method for reading a microwave readable barcode formed from a pattern of dielectric material. The dielectric pattern creates a strong microwave contrast with the surrounding media selectively resonating with or scattering an interrogating microwave signal. Dielectric bars can be fabricated by inkjet printing, injection, spraying, drawing or any other technique. Barcode information is encoded using different lengths, angles, or positions of dielectric bars. A microwave readable dielectric barcode system includes a barcode fabricated from a dielectric material, a transmitter with an antenna, and a sensor that senses the effect produced by the dielectric barcode on the microwave signal. The dielectric barcode system can use multiple microwave signals that differ in one or more respects, such as polarization or frequency.

CLAIM OF PRIORITY

This application claims priority under 35 U.S.C. § 119 as a continuationof Swedish Patent Application No. 0402996-3, titled “MICROWAVE READABLEFERROELECTRIC BARCODE” to the same inventive entity as this application,and filed Dec. 9, 2004 in the English language, which is herebyincorporated by reference in its entirety. This application also claimspriority under 35 U.S.C. § 119 of U.S. Provisional Application Ser. No.60/594,961, titled “MICROWAVE READABLE FERROELECTRIC BARCODE” to thesame inventive entity as this application, and filed May 23, 2005, whichis also hereby incorporated by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to barcodes, to the methods and materialsto fabricate such barcodes, as well as to the methods of how to writeand read the information represented by barcodes. In particular, theinvention relates to barcodes that are composed of dielectric materials.

BACKGROUND OF THE INVENTION

Today uniform product code (UPC) labels are on practically every productproduced in the world. Optical barcodes have become so widely acceptedbecause of their low production costs, device complexity, and highdurability. These same properties which caused their success now limittheir usefulness in commercial applications. The simple design has lowproduction costs, but is severely limited in the amount of data it canrepresent. The design also allows for simple and cheap detection throughoptical reading systems. However, optical reading systems require adirect, unobstructed path for light to be emitted onto the barcode andthen reflected back to the sensor. This unobstructed (i.e.,“line-of-sight”) property of optical read barcodes limits theirusefulness. For example, to conduct inventory management, objects mustbe placed in a specific physical location for their identificationinformation to be read.

To combat the “line-of-sight” problem posed by traditional barcodes,radio-frequency identification solutions have been developed.Radio-Frequency Identification (RFID) tags store and transmitidentification information that is similar to the information stored inbarcodes. A RFID system consists of an interrogation device thatbroadcasts a radio signal and a RFID tag which receives said radiosignal. With a passive RFID tag, the radio signal power itself is usedto power-up a small microchip within the tag, which then transmits itsunique identification code back to the interrogation device. The radiowaves used to interrogate RFID tags for can pass through many materials,therefore solving the “line-of-sight” issue present in optically readbarcodes.

RFID technology does, however, have its own problems. RFID tags can bedivided into two major categories: active and passive. Active RFID tagscontain their own power source which increases the distance in which itcan provide identification information. Problems with this type of taginclude cost of production due to the complexity of such a device aswell as maintenance issues, physical size and weight constraints, andpower consumption. Passive tags overcome cost and complexity issues, butin turn have greatly restricted operability and flexibility. Because amicrochip is embedded in an RFID tag, along with radio frequencyreceivers, front ends, and transmitters, the device complexity andassociated cost is much higher than that of optical barcodes.

Because of economic issues industry has been tentative in its adoptionof RFID. WalMart Corporation recently rolled out an initiative to haveall of their suppliers utilize RFID tagging to aid in their inventorymanagement and supply chain. While this program has benefits, it rasiesa new problem of data redundancy. Not only will each product now havebarcode identification information on it, but it will also have RFIDIdentification. The use of two identification methods for differentpurposes is costly and unneeded. Another problem with RFID technology isthe separation between an object and its identification information. Anobject is not directly identifiable as it was when a barcode wasembedded directly on the object itself. A tag is affixed to the object,therefore causing all relevant data to be associated with not the objectitself, but with a tag on the object. If a tag becomes separated fromthe object the identity of that object is lost.

One example of the problems associated with data separation caused byRFID technology can be seen in the field of livestock tracking. Sincethe advent of RFID solutions; the agriculture industry has beenattempting to utilize this technology for means of animal identificationin the form of a RFID tag affixed to an ear tag placed on the animal.(See U.S. Animal Identification Plan—National Identification DevelopmentTeam, available on the Internet at the U.S. AIP website informationpage, hereby incorporated by reference in its entirety.) Studies haveshown that approximately 10% of ear tags become separated from theanimal throughout its life cycle either by accidental separation, orthrough human removal. If data relative to an animal is associated witha RFID tag, and the tag becomes separated from the animal all dataassociated with that animal is also lost. Thus, with RFID technology,information is related not to the object itself, but to a tag which isthen associated with the object. This three party identificationsolution is more complex than a direct identification solution, and istherefore less reliable and less permanent.

One solution to all the aforementioned problems with the aboveidentification technologies is proposed in European Patent No.EP1065623A26 to J. F. P. Marchand, titled “Microwave Readable Barcode”(the EP '623 Patent”), which is hereby incorporated by reference in itsentirety. The EP '623 Patent describes a microwave readable barcode thatconsists of conductive bars made from a conductive ink or conductivefoil. Barcode information can be encoded using conductive bars ofdifferent lengths, different angles, or different positions. When thedevice is illuminated by a microwave signal, the encoded information canbe read through the attenuation, or non-attenuation, of the signal bythe conductive bars, and/or the scattering, or the non-scattering, ofthe microwave signal by the bars. A complete microwave readable barcodesystem includes conductive barcodes, a transmitter that radiates amicrowave signal onto the barcode, and a detector that senses themicrowave signal reflected from the conductive bars. Barcode systems canuse multiple microwave signals that differ in one or more respects, suchas polarization or wavelength.

While the approach disclosed in the EP '623 Patent solves two problems(the “line-of-sight” readability restrictions associated with opticalbarcode systems, and the data separation problem associated with RFIDtechnology), the disclosed microwave readable barcodes have limitationsand problems. The complexity of a device consisting of either conductivebars of conductive foil causes economic hurdles in the production of theprecursor material and in the fabrication of the conductive barcode.Therefore, embedding of a conductive barcode in an object is difficultand costly. The oxidation/corrosion processes limit the reliability ofthe conductive barcode. High cost of biocompatible metals makesconductive barcodes non-feasible for animal labeling. Also, it isimpossible to make an invisible conductive barcode.

Missing from the art is a barcode system that has increased commercialapplication with increased data representation, and overcomes theproblems of data separation, “line-of-sight” issues, and productionproblems. The present invention can satisfy one or more of these andother needs.

SUMMARY OF THE INVENTION

The present invention relates to a dielectric barcode which is a patternfabricated from a dielectric material, and a system for interrogatingthe dielectric barcode. In accordance with one aspect of the invention,a plurality of dielectric bars are arranged on or within a substrate.The dielectric bars are arranged in a spatial manner to encodeinformation.

In another aspect of the invention, the dielectric bars are formed froma dielectric material having a suspension of a metallic material in adensity insufficient to provide conductivity at an operating frequencyof a remote interrogator.

In accordance with another aspect of the invention, a barcodeinterrogation system comprises a dielectric barcode formed from aplurality of dielectric bars arranged on or within a substrate in aspatial manner to encode information, a signal transmitter connected toa first antenna so as to radiate an interrogation signal on thedielectric barcode, a signal receiver connected to an antenna so as toreceive a return signal from the dielectric barcode, and a processorconnected to the receive signal and operable to decode the encodedinformation.

In yet another aspect of the invention, the interrogation system isoperable to scan the interrogation signal through space to read thedielectric barcode. The system is capable to scan the signal by rotatingthe transmitting antenna, frequency shifting or phase shifting of thetransmitted signal.

These and other aspects, features, steps and advantages can be furtherappreciated from the accompanying figures and description of certainillustrative embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention together with further objects and advantages thereof, maybest be understood by making reference to the following descriptiontaken together with the accompanying drawings in which:

FIG. 1 illustrates a schematic rendition of a dielectric barcode systemembodying the present invention;

FIGS. 2 a-2 e illustrate several classes of microwave readabledielectric elements; and

FIGS. 3 a-3 c illustrate time variant reading of dielectric elements.

Throughout the drawings, the same reference characters will be used forcorresponding or similar elements.

DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS

By way of overview and introduction, presented and described areembodiments of a dielectric barcode which is a pattern fabricated from adielectric material. The dielectric barcode is readable by a microwavedevice. A dielectric barcode formed from any dielectric material in anyform is within the contemplation of this invention. For instance thedielectric barcode material can be in the form of an ink, a powder, or asolid material. An interrogating microwave signal propagates through thesurrounding media where it is effectively reflected and/or absorbed bythe dielectric barcode. Similar to an x-ray “shadow image” the patternmade from the dielectric material barcode can be visualized by thetransmitted or reflected microwave radiation.

In an embodiment of the invention, the dielectric barcode is formed froma dielectric material with a suspension of a ferroelectric material,having a high dielectric permittivity, within the dielectric material.The high dielectric permittivity of the ferroelectric material creates astrong microwave contrast with the media surrounding the ferroelectricbarcode at particular operating frequencies.

In another embodiment of the invention, the dielectric barcode is formedfrom a dielectric material provided with a fine powder suspensionsynthesized by chemical methods, and dispersed in suitable fluidicsystem to obtain a dielectric ink. A pattern is made from the dielectricink by inkjet printing, injection, spraying, drawing or any othertechnique. Injection can be done by an impetus injection mechanism wherethe dielectric material with the fine powder suspension is depositedbeneath a device's plastic subsurface or beneath the skin layer of ananimal to form a dielectric barcode. A non-inclusive list of suitablematerials for suspension within the dielectric material to form thedielectric inks includes, but is not limited to, heavy metals, heavymetal salts, piezo-electric ceramics, barium titanate (BaTiO₃), sodiumpotassium niobate (NaKNbO₃), and lead zirconium titanate (PbZrTiO₃ aka“PZT”). Metallic nano-particles (e.g., titanium nano-particles) are alsosuitable for suspension within dielectric materials to form thedielectric barcode. As is readily understood by a person of skill in theart, at different operating bands across the spectrum a particulardielectric material's perturbation to an electric field changes. Forexample, a dielectric material that is transparent at one operating bandmay become very lossy at another operating band. Thus, the suspension ofparticles within the dielectric material forming the dielectric barcodesoptimizes performance at the particular operating band of interest. Thedensity of these suspensions are enough to sufficiently alter therefractive and reflection properties of the dielectric material, but notdense enough to render the dielectric material conductive in theoperating band.

Due to dielectric permittivity (ε), the electromagnetic length in adielectric material is √ε shorter than in a vacuum. This phenomenonallows for the dielectric barcodes to be significantly miniaturized. Forexample, a resonant barcode composed of dielectric material with thedielectric permittivity ε˜1000 for 10 GHz (3 cm wavelength) operationwill be only a millimeter in size. Dielectric barcodes can betransparent/translucent in the visible light spectrum, though highlycontrasting for microwaves. In one embodiment to be used, as an example,for animal labeling, a biocompatible Na_(x)K_(1−x)NbO₃ ceramic could bethe candidate material from which to make dielectric barcodes.Biocompatible ferroelectric ceramics can be injected under the skinremaining there as a non-degradable tattoo for the entire life of theanimal. U.S. Pat. No. 6,526,984 to Nilsoon et al., issued Mar. 4, 2003,and titled “Biocompatible Material for Implants” discloses thebiocompatible ceramic Na_(x)K_(1−x)NbO₃, and is hereby incorporated byreference in its entirety.

FIG. 1 illustrates a schematic rendition of one embodiment of adielectric barcode system 10. The system 10 includes a microwavetransmitter 11 which emits a signal 12 that radiates outwards andtowards a substance 15 having a readable dielectric element 16. Themicrowave signal 12 has a wavelength 13 and is polarized such that theE-field is in the vertical direction 14. However, the wavelength andfield polarization are not limited to any one value or orientation, aswould be understood by a person of ordinary skill in the art. Thefrequencies of interest range from around 100 kHz to over 100 GHz, andfurther up to and including the TeraHertz (10¹² Hz) frequency band. Arange just above the operation of satellite dishes and mobile phones(about 90-100 GHz) through to adjacent to infrared frequencies used inremote controllers (about 30 THz), and more particularly, operatingfrequencies of about several Terahertz are believed to be beneficial.

In one embodiment, the readable element 16 is a ferroelectric bar formedfrom the biocompatible ceramic Na_(x)K_(1−x)NbO₃. So as to make thebarcode resonance and polarization sensitive to the interrogatingelectromagnetic wave of signal 12, the readable element 16 has a lengththat is one-half the wave-length 13, and an axis that is parallel to thedirection 14. Using the formula of wavelength equals the speed of lightover frequency, the wavelength necessary to read various sizes ofdielectric barcode elements can be calculated. Thus,λ=c/v where:   Eq. 1

-   -   λ=wavelength (microns)    -   v=frequency (Hertz), and    -   c=3*10ˆ14 μm/sec (speed of light).

The required wavelength necessary to read a dielectric barcode elementof a specific size can be calculated. For an embodiment operating in theTeraHertz operating band, a frequency of 1.0 THz has a wavelength of 300μm, requiring a readable element 16 to have a length of 150 μm. Formultiple readable elements in a single barcode, the readable elementswould be spaced apart one-half the wavelength. From this information itis possible to calculate the overall width of this embodiment of amicrowave readable barcode from the following equation:W=N(λ/2)+(N−1)(λ/2) μm where:   Eq. 2

-   -   W is the barcode width in microns,    -   N is the number of readable elements forming the barcode, and    -   λ=wavelength (microns).

Thus, applying Equation 2, the width of a barcode tag having 96 bitswould be 96*150 (the elements)+95*150 (spaces betweenelements)=14400+14250=28650 μm=28.65 mm long.

With reference to FIGS. 3 a-3 c, a time variant reading of the microwavereadable barcode is illustrated. To resolve a tag of more than onedimension (i.e., a tag utilizing a 2-dimensional encoding scheme) aspatial relationship (e.g., an interstitial gap) must be establishedbetween elements. To accomplish this, a single microwave source can scanthe tag area relative to the time constant to achieve a 2-D “image” ofthe tag, which can then be processed to extract the information therein.Thus, by collecting the readings relative to time and position an imageof the barcode can be reconstructed and its information extracted.

There are many schemes known to a person of ordinary skill in the art toachieve a scan of the tag area. For example, an antenna (not shown)connected to the microwave transmitter 11 can be physically rotated inat least one degree of freedom (e.g., azimuth, vertical, roll, pitch andyaw) to move the peak of the transmitted signal 12 across a group ofdielectric elements 16 which form a barcode. Alternatively, the phase orthe frequency of the transmitted signal 12 can be varied to cause thebeam collimation to move in spatial relation to the location of thedielectric elements. The antenna can be composed of an array ofelements, where the inter-element phasing is controlled to adjust thebeam's spatial location. These and other implementations and methods ofscanning a transmitted signal through space are within the contemplationof the present invention.

With reference to FIG. 1, when the transmitted signal 12 strikes thedielectric element 16, the signal is partially scattered and partiallyattenuated. The scattered portion 18 of the signal 12 can be sensed by asensor 20. Sensor 20 itself can be the same antenna connected to thetransmitter 11, or a different sensor implementing the same or differenttechnology as the antenna. The sensor further includes a processorcapable of decoding the encoded information present in the dielectricbarcode. As is readily understood, sensor 20 can be implemented byseparate components of an antenna, a processor, and an output interface.

If the sensor 20 receives a scattered signal it determines that adielectric readable element exists. In that case the sensor 20 producesa predetermined output signal. In a binary information system, thepredetermined output signal indicates the presence of a readable elementand could be a one or a zero. FIG. 1 also shows a dielectric bar 17 thatis much thinner than the readable element 16. The dielectric bar 17would only slightly scatter the signal 12. The sensor 20 would thenproduce another output signal, say a zero, based upon a missing (lowscattered) signal. Of course, the dielectric bar 17 might be missingaltogether.

While the foregoing discusses the use of binary information (zeros andones), the present invention is not limited to only one type of encodingscheme. In another embodiment, a first ferroelectric bar of one lengthand/or orientation can represent any member of a set (such as a letteror a number). Further, a second dielectric bar of another length and/ororientation can represent another member of the set, and a third andother dielectric bars of other lengths and/or orientations mightrepresent other members, and so on. By varying the wavelength and/orpolarization of transmitted signal 12 these differing lengths andorientations can be sensed and the corresponding set members identified.

Inkjet printing technique can be applied to deposit dielectric layersand structures consisting of nano-sized dielectric particles. Thesedielectric particles can be synthesized by chemical methods andsuspended in a suitable fluidic system. The rheological parameters ofthe fluids can be adjusted for inkjet printing. The resultingmicron-scale patterns can be obtained with a high reproducibility andstructure control. The dielectric local structure of the patterns can bestudied by using a local dielectric probe technique as well as atnano-scale atomic force microscopy with a local capacitance probe can beemployed. The deposited structures will have a chain-like self-alignmentof the dielectric particles. Potential applications of this fast andversatile process are the production of low- and medium densitydielectric mass storage patterns on almost any kind of substrate and fordielectric character recognition purposes. Printed patterns with minimalstructure dimensions in the range of 50-100 μm are easy to achieve.

The illustrated embodiments of the present invention attempt to overcomethe problems associated with the conventional identification methodsdiscussed above. Dielectric barcodes solve the readability problemthrough utilizing microwaves as the method of extracting informationfrom the tag. A dielectric barcode also solves the problem of dataredundancy associated with the use of optical barcodes in conjunctionwith RFID technology. Dielectric barcodes can be constructed to utilizenot only optical reading systems, but also quasi-optical systems (i.e.,systems operating at millimeter wavelength bands) similar to that ofRFID technology to be remotely identified as well. Dielectric barcodesovercome the problem of data separation as well. Since dielectricbarcodes can be directly embedded or printed on an object in a similarfashion to optical barcodes instead of embodied in a tag which isaffixed to an object, the identification information comes directly fromthe object itself instead of from a tag placed on the object.

In particular, a non-exhaustive list of advantages offered over theprior art by the various embodiments of the present invention includes:

-   -   providing cheap and reliable material for radio-frequency        identification tags;    -   reducing the number of extra elements and eliminating power        consuming units connected to the device, thereby allowing a        small overall device size and complexity;    -   providing advanced encoding of the identification information in        the form of spatial and temporal dispersion of the        reflected/transmitted interrogating microwave signal;    -   allowing biocompatible barcode labeling of creatures;    -   providing invisible barcode patterns and/or a barcode pattern        deposited beneath the surface of the coded sample.

Thus, while there have been shown, described, and pointed outfundamental novel features of the invention as applied to severalembodiments, it will be understood that various omissions,substitutions, and changes in the form and details of the devicesillustrated, and in their operation, may be made by those skilled in theart without departing from the spirit and scope of the invention.Substitutions of elements from one embodiment to another are also fullyintended and contemplated. It is also to be understood that the drawingsare not necessarily drawn to scale, but that they are merely conceptualin nature. The invention is defined solely with regard to the claimsappended hereto, and equivalents of the recitations therein.

1-15. (canceled)
 16. A method of interrogating a barcode comprising thesteps of: providing a dielectric barcode formed from a plurality ofdielectric bars arranged in a spatial manner so as to encodeinformation; providing a signal generation and reception system capableof transmitting an interrogation signal and receiving a return signal;transmitting an interrogation signal; receiving a return signal from thedielectric barcode; and processing the return signal to extract theencoded information.
 17. The method of claim 16 further including thestep of scanning the interrogation signal through a volume of space. 18.The method of claim 16, wherein the dielectric barcode is provided byone of printing, spraying, and injecting.
 19. The method of claim 16,further including the step of creating the dielectric bars from adielectric material having a suspension of metallic material in adensity insufficient to provide conductivity at a frequency of theinterrogation signal.
 20. The method of claim 16, wherein thetransmitting step transmits a signal in the range of about 90 GHz toabout 30 THz.